1. Field of the Invention
The present invention relates to a catalyst for dimethyl ether, a method for producing the catalyst, and a method for producing dimethyl ether by using the catalyst.
2. Description of the Related Arts
There are several known methods for manufacturing dimethyl ether starting from a mixed gas of carbon monoxide, carbon dioxide, and hydrogen under the presence of a catalyst suspended in a solvent.
For example, JP-A-2-9833 (the term xe2x80x9cJP-A-xe2x80x9d referred to herein signifies xe2x80x9cUnexamined Japanese patent publicationxe2x80x9d), JP-A -3-181435, JP-A-3-52835, JP-A-4-264046, WO 93/10069 disclose methods for manufacturing dimethyl ether or a mixture of dimethyl ether and methanol through the contact of a synthesis gas with a mixture of a methanol synthesis catalyst and a methanol dehydration catalyst suspended in an inert liquid.
The method disclosed in JP-A-2-9833 is a method of direct synthesis of dimethyl ether from a synthesis gas, which method comprises the step of contacting a synthesis gas consisting of hydrogen, carbon monoxide and carbon dioxide with a solid catalyst, or reacting the synthesis gas react under the presence of the solid catalyst to conduct catalytic synthesis of dimethyl ether from the synthesis gas, wherein the synthesis gas undergoes catalytic action under the presence of the solid catalyst system, and wherein the solid catalyst is a single catalyst or a mixture of plurality of catalysts which are suspended in a liquid medium in a three-phase (slurry phase) reactor system, and wherein the three-phase reactor system comprises at least a single three-phase reactor.
The method disclosed in JP-A-3-181435 is a method for manufacturing dimethyl ether from a mixed gas of carbon monoxide and hydrogen, or a mixed gas of carbon monoxide and hydrogen and further containing carbon dioxide and/or water vapor, wherein a catalyst is used in a slurry form by suspension thereof in a solvent.
The method disclosed in JP-A-3-52835 is a method of dimethyl ether synthesis characterized in that a synthesis gas is reacted under the presence of a solid methanol synthesis catalyst to produce methanol, and that the produced methanol is reacted under the presence of a solid dehydration catalyst to produce dimethyl ether. According to the method, dimethyl ether is synthesized from a synthesis gas consisting of hydrogen, carbon monoxide, and carbon dioxide. That is, the synthesis gas is contacted with a solid catalyst system comprising a methanol-synthesizing ingredient and a dehydrating (ether-forming) ingredient, wherein the solid catalyst system is a single catalyst or a mixture of plurality of catalysts in a three-phase (liquid phase) reactor system, and wherein the reactor system is controlled to keep the minimum effective methanol rate to at least a level of 1.0 g-mole of methanol per 1 kg of catalyst per hour.
The method disclosed in WO 93/10069 is a method for manufacturing dimethyl ether from a mixed gas containing carbon monoxide and either or both of water and water vapor, or from a mixed gas containing carbon monoxide and either or both of water and water vapor and further containing carbon dioxide, wherein a catalyst is used in a form of solvent slurry, which catalyst is prepared by pulverizing a mixed catalyst containing at least zinc oxide and, copper oxide or chromium oxide, and aluminum oxide, by adhering these ingredients together under pressure, and by pulverizing them again to suspend in the solvent.
On the other hand, dimethyl ether is synthesized generally in a fixed bed system. There is a known catalyst for a fixed bed system, which catalyst is prepared by depositing a methanol synthesis catalyst onto a support of metallic oxide such as alumina, then by calcining them together. (JP-A-2-280386)
The methods for manufacturing dimethyl ether disclosed in JP-A-2-9833, JP-A-3-52835, JP-A-4-264046, and JP-A-3-181435, however, raise problems such that the two kinds of or three kinds of catalysts suspended in a solvent separate from each other in the reactor owing to the difference in specific gravity among the methanol synthesis catalyst, the methanol dehydration catalyst, and the water gas shift catalyst, which induces a distribution in catalyst concentration or deposition of one of these catalysts, thus significantly degrading the use efficiency of the catalysts.
The catalyst disclosed in WO 93/10069 is prepared by integrating the above-described three kinds of catalysts by means of a mechanical method. These types of catalysts also raise a problem, that during a period of use in a slurry state, the catalyst particles separate from each other to induce a distribution in catalyst concentration and catalyst deposition.
It is an object of the present invention to provide a catalyst suitable for producing dimethyl ether at a high yield and a method for producing the catalyst, and to provide a method for producing dimethyl ether at a high space time yield.
To attain the object, the present invention provides a first catalyst suitable for producing dimethyl ether, the catalyst comprising:
alumina particles having an average size of 200 xcexcm or less;
a layer comprising a methanol synthesis catalyst, the layer being formed around each of the alumina particles; and
the methanol synthesis catalyst having a weight ratio of 0.05 to 5 to a weight of the alumina particles.
In the first catalyst, the average size of the alumina particles is preferably 1 to 100 xcexcm. The average size of 1 to 50 xcexcm is more preferable.
The methanol synthesis catalyst may comprise copper oxide, zinc oxide and alumina. It is desirable that a weight ratio of the copper oxide:the zinc oxide:the alumina is 1:0.05 to 20:0 to 2. The methanol synthesis catalyst may comprise zinc oxide, chromium oxide and alumina. It is desirable that a weight ratio of the zinc oxide:the chromium oxide:the alumina being 1:0.1 to 10:0 to 2.
The first catalyst suitable for producing dimethyl ether is produced by the following method comprising the steps of:
forming a layer comprising a methanol synthesis catalyst around each of alumina particles; and
washing the alumina particles, around which the layer was formed, with an acid aqueous solution.
The forming of the layer may comprise:
forming a slurry by introducing the alumina particles into an aqueous solution containing a metallic salt of active element of the methanol synthesis catalyst;
heating the slurry; and
neutralizing the heated slurry with a base solution, thereby the active element of the methanol synthesis catalyst being deposited around each of the alumina particles.
The deposition of the active element of the methanol synthesis catalyst is preferably carried out at a temperature of 50 to 90xc2x0 C.
Dimethyl ether is produced by using the first catalyst. A method for producing dimethyl ether comprising the steps of:
providing the first catalyst suitable for producing dimethyl ether, the catalyst;
forming a slurry by introducing the catalyst into a solvent; and
introducing a mixed gas comprising carbon monoxide and hydrogen into the slurry.
The present invention provides a second catalyst suitable for producing dimethyl ether, the catalyst comprising:
alumina particles having pores;
deposits which exist inside the pores; and
the deposits comprising copper oxide, zinc oxide, and alumina.
It is preferable that the alumina particles have an average size of 200 xcexcm or less. A weight ratio of the copper oxide:the zinc oxide:the alumina is preferably 1:0.05 to 20:0 to 2.
The second catalyst suitable for producing dimethyl ether is produced by the method comprising the steps of:
(a) introducing an alumina having pores into an aqueous solution containing a copper salt, a zinc salt and an aluminum salt for impregnating the pores with the aqueous solution;
(b) vaporizing the aqueous solution on a surface of the alumina;
(c) contacting the alumina subjected to the step (b) with a solution containing a deposition agent for hydrolyzing the copper salt, the zinc salt and the aluminum salt to copper hydroxide, zinc hydroxide and aluminum hydroxide and for depositing the copper hydroxide, the zinc hydroxide and the aluminum hydroxide within the pores of the alumina;
(d) washing the alumina subjected to the step (c); and
(e) calcining the washed alumina.
Dimethyl ether is produced by using the second catalyst. A method for producing dimethyl ether comprising the steps of:
providing the second catalyst suitable for producing dimethyl ether;
forming a slurry by introducing the catalyst into a solvent; and
introducing a mixed gas comprising carbon monoxide and hydrogen into the slurry.
The present invention provides a third catalyst suitable for producing dimethyl ether, the catalyst comprising:
a methanol synthesis catalyst;
a methanol dehydration catalyst; and
a binder for integrating the methanol synthesis catalyst and the methanol dehydration catalyst.
The methanol synthesis catalyst may comprise copper oxide, zinc oxide and alumina. A weight ratio of the copper oxide:the zinc oxide:the alumina is preferably 1:0.05 to 20:0 to 2. Also, the methanol synthesis catalyst may comprise zinc oxide, chromium oxide and alumina. A weight ratio of the zinc oxide:the chromium oxide the alumina is preferably 1:0.1 to 10:0 to 2. The methanol dehydration catalyst may be at least one selected from the group consisting of xcex3-alumina, silica-alumina and zeolite. The third catalyst may further comprise a water gas shift catalyst. The water gas shift catalyst may comprise iron oxide and chromium oxide. The binder may be alumina sol or clay.
Dimethyl ether is produced by using the third catalyst. A method for producing dimethyl ether comprising the steps of:
providing the third catalyst suitable for producing dimethyl ether;
forming a slurry by introducing the catalyst into a solvent; and
introducing a mixed gas comprising carbon monoxide and hydrogen into the slurry.
Further, the present invention provides a method for producing a catalyst suitable for producing dimethyl ether, the method comprising the steps of:
(a) preparing a methanol synthesis catalyst, a methanol dehydration catalyst, a water gas shift catalyst and a solvent;
(b) calculating an A value regarding to the methanol synthesis catalyst, the methanol dehydration catalyst and the water gas shift catalyst using an average particle size of the catalyst, a particle density of the catalyst and a density of the solvent, the A value being defined by the following equation:
A=D2(Pxe2x88x92S),
xe2x80x83where
D denotes the average particle size of the catalyst, (cm),
P denotes the particle density of the catalyst, (g/cm3), and
S denotes the density of the solvent, (g/cm3),
(c) controlling at least one of the group consisting of the average particle size of the catalyst, the particle density of the catalyst and the density of the solvent to maintain differences in the A values within xc2x11xc3x9710xe2x88x926 g/cm among the methanol synthesis catalyst, the methanol dehydration catalyst, and the water gas shift catalyst;
(d) after the step (c), suspending the methanol synthesis catalyst, the methanol dehydration catalyst, and the water gas shift catalyst in the solvent.
Furthermore, dimethyl ether can be produced by the method comprising the steps of:
providing a mixed gas containing carbon monoxide and at least one selected from the group of hydrogen and water vapor;
contacting the mixed gas with a first catalyst consisting essentially of a methanol synthesis catalyst, a dehydration catalyst and a water gas shift catalyst; and
contacting the mixed gas, which contacted with the first catalyst, with a second catalyst consisting essentially of at least one selected from the group of a dehydration catalyst and a water gas shift catalyst.
Moreover, dimethyl ether can be produced by the method comprising the steps of:
(a) reacting a raw material gas containing carbon monoxide and hydrogen in the presence of a catalyst to produce a reaction gas including dimethyl ether, carbon dioxide, carbon monoxide and hydrogen;
(b) separating the reaction gas into the carbon monoxide and the hydrogen, and the dimethyl ether and the carbon dioxide;
(c) recycling the carbon monoxide and the hydrogen which were separated from the reaction gas in the step (b);
(d) removing the carbon dioxide from the dimethyl ether and the carbon dioxide of the step (b) to gain the dimethyl ether; and
(e) recycling the dimethyl ether which was gained in the step (d) to the step (b).
Further, dimethyl ether can be produced by the method comprising the steps of:
preparing a slurry which is produced by dispersing a dimethyl ether synthesis catalyst into a medium oil;
contacting a raw material gas containing carbon monoxide and hydrogen with the slurry to produce a product gas containing a vaporized medium oil;
cooling the product gas to condense the vaporized medium oil;
obtaining dimethyl ether from the product gas from which the vaporized medium oil was condensed;
removing a catalyst-deactivation ingredient from the condensed medium oil; and
recycling the medium oil, from which the catalyst-deactivation ingredient was-removed, to the step of preparing the slurry.
Further, the present invention provides an apparatus for producing dimethyl ether comprising:
a slurry-bed reactor filled with a dimethyl ether synthesis catalyst and a medium oil therefor;
a condenser for condensing a vaporized medium oil discharged from the reactor;
an adsorber for removing a catalyst-deactivation ingredient from the medium oil condensed in the condenser; and
recycle means for recycling the medium oil to the slurry-bed reactor.